In this question, you're solving for a.
Solve for a:
-8(1 - a) =-7 -(1 - 3a)
use the distributive property
-8 + 8a = -7 -(1 - 3a)
-8 + 8a = -7 - 1 + 3a
combine like terms
-8 + 8a = -8 + 3a
subtract 3a from both sides
-8 + 5a = -8
add 8 to both sides
5a = 0
divide both sides by 5
a = 0